Various types of fluids are used in applications in the oil and gas industry, paint industry, plastics industry, pharmaceutical industry, and others. Understanding rheology of emulsions, slurries and suspensions is desirable in these applications. Typically, as two or more immiscible fluids flow through a pipeline, reactor, column, and so on, the mixing of the fluids varies at different locations within the system due in part to varying shear rates. This flow phenomenon may result in formation of emulsions and suspensions that are substantially stable in shear environment but may separate out into their constituents as the effect of shear is reduced. It is desirable to determine in-situ rheological properties, such as viscosity for such fluid systems, to appropriately design a part or the whole of a system accordingly.
Conventional techniques for measuring the rheological properties of multi-phase fluids such as emulsions and slurries include mixing them in a separate pre-mixer. The emulsion formed after the mixing is subsequently transferred to a cup and bob assembly of a rheometer and the viscosities may be measured using the rheometer for different shear rates. However, mixing of the fluids using the conventional cup and bob systems is sometimes poor, especially at low shear rates. Moreover, pre-mixed emulsions are often substantially unstable. Furthermore, in a conventional, vertical cup and bob rheometer, shearing takes place in a direction normal to the spin axis of the cup and bob assembly (and tangential to an infinite series of circles concentric with the cup/bob). Radial mixing is usually not expected in such scenarios. In certain cases, if multi-phase fluids are used, the fluids may also not mix with one another due to variation in the densities of the fluids resulting in settling, with the densest fluid at the bottom, and the lightest fluid at the top, thereby resulting in inaccurate measurements.